1. Field of the Invention
This invention relates to the field of hand saws and more particularly, to a D-shaped handle for coping saws.
2. Description of the Prior Art
Coping saws have been prevalent in the prior art for some time. The earliest forms utilized the characteristic bulbous straight handle as an auxiliary handle and as a means of rotating the saw blade relative to the saw frame. Initially, the frame was grasped to transfer force to the cutting edge of the blade and to move the cutting edge across a work surface. In these early designs, two bulbous straight handles were located on opposite shanks of an open, rectangular shaped frame so that a blade held between the two shanks could be axially rotated by rotating the handles. To effect a cut, rotation of the blade was often necessary so that the saw frame did not interfere with the stroke. Today, the form of coping saw which is most prevalent utilizes a bulbous straight handle for three functions: 1) as a means for tightening a blade on a U-shaped frame; 2) as a means for transferring downward force to the blade during the cutting stroke; and 3) as a means for rotating the blade relative to the saw frame. Specifically, the first end of the blade is rotatingly attached to the first open end (shank) of the U-shaped frame. The second end of the blade is held by a blade holder which has a threaded shaft extending through an opening on the opposite, second open end (shank) of the frame. The bulbous handle is axially threaded to allow it to engage the threaded shaft so that as the handle is tightened on the shaft, the blade is tensioned between the first and second shanks of the frame. In this configuration, the axis of the handle is aligned with the axis of the blade, and the blade can be rotated relative to the frame to allow the frame to be positioned so as not to interfere with a cut.
Straight handles such as the one described above are undesirable because of the rapid fatigue of the hand created by the unnatural and extended position of the hand as it grasps the handle. Specifically, when grasping a straight handle, at least the thumb, index finger and the middle finger must apply a pinching grip to the handle, while at the same time the muscles in the outer portion of the hand are extended. This exertion often results in fatigue and soreness of the muscles in the hand and wrist. In day to day use, this strain on the hand and wrist can lead to Carpal tunnel syndrome, a condition that can permanently damage the nerves of the hand and wrist.
Additionally, this type of grip may inhibit the user from taking advantage of the faster cutting, coarser-toothed blades because the operator is unable to adequately transfer force to the cutting edge of the blade while maintaining control of the saw. Typically, a slow cutting, 20 teeth per inch (TPI) blade is used for the most demanding copes in terms of effort and skill. Sometimes, a 15 TPI blade may be used, but rarely is the fastest cutting, 10 TPI blade used because it is difficult to maintain a grip on the straight handle and attain the leverage needed to direct the cut with such coarse blades. It is not unusual for coarser-toothed blades to become jammed in the saw kerf such that the user loses grip of the handle.
One type of handle which is old and well known in the art for use with other types of saws is the pistol grip handle. This type of handle has been utilized to increase the downward force which can be applied to the cutting edge of a saw blade so that cutting times can be decreased. Pistol grip handles also reduce a portion of the hand fatigue associated with the use of straight handles. The prior art is replete with examples of pistol grip handles, especially in combination with hacksaws. U.S. Pat. No. 1,470,040, issued to Whitehead, teaches a pistol grip handle which can be affixed to a bulbous straight handle to convert the straight handle to a pistol grip. The ends of the pistol grip are clamped around the straight handle and secured with fasteners so that the pistol grip handle angles down and away from the straight handle in the same plane as the saw blade. One drawback to this handle is that such a handle is difficult to manipulate because it attaches in line with the axis of the blade and extends down from this axis, creating a moment about the point of attachment.
U.S. Pat. No. 2,014,722, issued to Damon, describes a pistol grip handle which can be permanently attached to a standard U-shaped or L-shaped hacksaw frame. The handle is rigidly fixed at two points on the upper corner of the frame such that the portion of the handle which is gripped extends downward, adjacent the frame and in the same plane as the frame and the saw blade. The handle is formed of strip steel of U-shaped cross section so that it is resilient and will yield slightly in the grip of the hand to avoid fatigue.
Another pistol grip handle is disclosed in U.S. Pat. No. 2,303,705. Again, the handle is rigidly fixed to a saw frame at two points on the frame so that the handle is angled down and away from the saw blade in the same plane as the blade. At least one shank of the handle is intended to be fixed to the saw frame under a certain degree of strain so that the handle has a certain inherent springiness.
Although the above mentioned pistol grip handles generally provide the optimum transfer of force to cutting blades, the angle of these handles relative to the saw blades limits the operators' ability to manipulate the saws to effect various cuts. Specifically, pistol grip handles are oriented on a downward angle, sloping away from the saw blade. This configuration facilitates cuts made in only one direction, i.e., toward the operator. When a pistol grip handle is properly grasped, the cutting edge of the saw must be substantially parallel with the operator's forearm, making it difficult and very uncomfortable to grip the saw handle and make a cut away from the operator.
However, because of the delicate and intricate nature of the work performed with coping saws, the required cuts are often multi-directional, such that the direction of the blade relative to the operator must often be altered to complete the cut. Although it is most desirable to make a single, uninterrupted cut, pistol grip handle saws render such a task difficult because of the manner in which the handle is grasped by the operator. Therefore, an operator may be required to interrupt a cut and reposition the saw blade to complete the cut. For example, if an operator is cutting a 180 degree symmetric curve, a first cut may be made toward the operator through the first 90 degrees of the arc. At this point along the cut, the cutting is interrupted and the saw is repositioned so that a second cut through the remaining 90 degrees can also be made toward the operator. Interrupting cutting, backing the saw blade out of the cut and repositioning the saw in the manner is often tedious and time consuming. Thus, these types of handles make it difficult to complete a single cut without interrupting the cut to reposition the saw and handle relative to the operator. Pistol grip handles, therefore, would be of little used in combination with coping saws or similar saws which are used to make multidirectional cuts.
Therefore, it is desirable to provide a handle for coping and similar saws which maximizes the force applied to the cutting edge of a saw blade, while minimizing hand fatigue. The handle should be easily manipulated for multidirectional cuts without the need for interrupting the cut to reposition the saw. It is further desirable to provide a handle which can be attached to a standard U-framed coping saw such that the handle can be rotated with the saw blade relative to the frame. Additionally, such a handle should be inexpensive and easily attached.